/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.basics;import java.io.*;  // We're doing input, so import I/O classes/** * This program reads lines of text from the user, encodes them using the  * trivial "Rot13" substitution cipher, and then prints out the encoded lines. **/public class Rot13Input {    public static void main(String[] args) throws IOException {        // Get set up to read lines of text from the user        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));        for(;;) {                                    // Loop forever            System.out.print("> ");                    // Print a prompt            String line = in.readLine();               // Read a line            if ((line == null) || line.equals("quit")) // If EOF or "quit"...                break;                                 // ...break out of loop            StringBuffer buf = new StringBuffer(line); // Use a StringBuffer            for(int i = 0; i < buf.length(); i++)      // For each character...                buf.setCharAt(i, rot13(buf.charAt(i)));// ..read, encode, store            System.out.println(buf);                   // Print encoded line        }    }        /**     * This method performs the Rot13 substitution cipher.  It "rotates"     * each letter 13 places through the alphabet.  Since the Latin alphabet     * has 26 letters, this method both encodes and decodes.     **/    public static char rot13(char c) {        if ((c >= 'A') && (c <= 'Z')) {  // For uppercase letters            c += 13;                       // Rotate forward 13            if (c > 'Z') c -= 26;          // And subtract 26 if necessary        }        if ((c >= 'a') && (c <= 'z')) {  // Do the same for lowercase letters            c += 13;            if (c > 'z') c -= 26;        }        return c;                        // Return the modified letter    }}